The present invention relates to a method for the production of a thin-film solar cell array in which a plurality of individual thin-film solar cells are applied on a substrate. The individual thin-film solar cells are thereby deposited one above the other in regions so that an overlapping region is produced from respectively one pair of two individual thin-film solar cells; in this region, a series connection of the two thin-film solar cells forming the pair is present. In addition, the thin-film solar cell array has a transition region in which the thin-film solar cell applied on the first solar cell is converted into a layer situated below.
In scaling up solar cells, organic light-emitting diodes and batteries, the problem exists that the current increases proportionally to the surface area. Since the ohmic power loss increases quadratically with the current, clear limits for the size of individual cells result herefrom. This problem is generally solved by                1. the use of very conductive strip conductors (usually silver) and also        2. the series connection of cell elements to form a module.        
In the latter case, the current remains constant when increasing the module surface area and the voltage increases proportionally to the size of the module. However, a significant loss of active surface area and hence of efficiency is associated herewith.
For small-surface applications, the problem often exists of achieving sufficiently high voltage on a small surface area. In the case of a conventional connection, this necessarily leads to a very high relative surface area loss and hence efficiency loss. This problem can be solved by stacking a plurality of partially transparent solar cells/oLEDs/batteries in order to achieve a higher voltage and lower current densities, as a result of which fewer cell strips are required. However, the problem arises that all the sub-cells must deliver/consume the same current. However this can only be ensured, e.g. for solar cells, by adapting the layer thicknesses for a specific spectrum.
In the case of thin-film solar cells, generally a monolithic series connection is produced in order to avoid ohmic power losses in the transparent electrode by the individual layers of the solar cell being structured periodically in individual strips, specific layers having a defined overlap in order to connect the plus pole of one strip to the minus pole of the adjacent strip electrically without a short circuit being produced between the poles of one strip. A similar process can also be undertaken for large-surface oLEDs or batteries. These connection regions do not provide any current/light and hence represent a surface area- and hence power-/efficiency loss. Since the respective layers must be structured at least partially before coating with the further layers, this connection places high demands on the repetition precision or register accuracy. At least three, more likely five times the minimum structural size or tolerance is required for the connection. The more layers the stack comprises, the more critical this problem becomes.
A further possibility is the production of individual cell elements, one of the contacts being guided on the rear-side and these cell elements being fixed to each other, shingle-like, with a small overlap (DE 10 2008 049056, DE 100 20 784). As a result, the surface area loss is significantly reduced. Of disadvantage hereby are the high requirements on the positional precision, relatively complex handling of the generally small individual elements and also the resulting greatly uneven topography from which a more complex encapsulation results and also mechanical weakened points are produced.
A normal array of thin-film solar cells which is known from the state of the art is described in FIG. 1. With respect to the meaning of the reference numbers and the terminology which is used, reference is made to the definitions for FIG. 1 ff. which are given further on. A plurality of thin-film solar cells (I and II) which are applied adjacently in x-direction is illustrated. The respective thin-film solar cells thereby have respectively a rear-side electrode (1), a photoactive layer (2) applied over the electrode (1) in z-direction and also a second electrode and/or a conversion layer (3) applied hereon. All of the components of such thin-film solar cells, illustrated schematically in FIG. 1, i.e. electrode (1), photoactive layer (2) and also conversion layer (3), can thereby be configured in one layer, however they can also consist of a plurality of layers (e.g. a conductive layer and a charge carrier-selective layer, likewise a plurality of layers is possible. For example, likewise the photoactive layer (2) can have an inner structure (e.g. two or more layers one above the other or an interpenetrating network made of two or more materials). For example, it is likewise possible that the electrodes can comprise a conversion layer. The partial solar cells can respectively also be multiple solar cells (multijunction solar cells). Such a multitude of possibilities for the individual components of the thin-film solar cells are available both for the thin-film solar cell known from the state of the art according to FIG. 1 and also all of the subsequently illustrated embodiments of the thin-film solar cells produced with the method according to the invention.
The production of current in the case of the thin-film solar cell array illustrated in FIG. 1 is restricted to the surface areas in which all of the three layers (rear-side electrode, photoactive layer and also second electrode and/or conversion layer) are disposed situated one above the other. The respective individual layers of the individual solar cells are thereby configured in steps (in FIG. 1, in the case of the respective solar cells I and II, illustrated respectively on the left) in order to avoid electrical short circuits of the solar cells. In one region (L), a series connection of the individual solar cell modules I and II is effected, in which the upper electrode and/or conversion layer (3I) of the first solar cell (I) is contacted with the rear-side electrode (1II) of the second thin-film solar cell (II). Such a series connection is termed in the state of the art “monolithic series connection”. It is detectable that no solar cell is configured in region (L) since, in this region, the three layers (1, 2 and 3) forming one respective solar cell are not disposed situated one above the other. The surface area of such a thin-film solar cell array configured in region (L) cannot hence be used for current production.